Hyponaetremia Flashcards
What is Hyponatremia?
Serum Sodium < 136mmol/l
What are the symptoms of Hyponatremia?
They are caused my decreased ECF osmolality so water does intracellular - this causes cerebral oedema and:
- Lethargy
- Confusion
- Coma
- Convulsions
What are the causes of hyponaetremia?
What is the role of ADH/Vasopressin in hyponatremia?
What does it do?
It is released in times of stress or dehydration and causes the following things:
V1 - Vasoconstriction
V2 - Increased water uptake via aquaporins
Net effect of retaining fluid and keeping BP up
How can true volume depletion and high ADH lead to hyponatremia?
Vomiting and diarrhoea causes volume depletion and release of ADH - can lead to hyponatremia
What is hypervolemic hyponaetremia?
How does ecstasy lead to high ADH and hyponatremia?
It directly increases ADH and increases thirst which leads to hyponatremia
How does SIADH lead to high ADH and hyponatremia?
Related to lung diseases and increased ADH levels causes relative hyponaetremia
How does marathon running lead to increased ADH and hyponatremia
Exercise stimulated ADH despite loss of salt in sweat.
This plus increased water uptake causes hyponaetremia
What could be the causes hyponatremia and low ADH?
Polydypsia eg alcohol
Renal failure - not responding to ADH so it stops being produced
What physical signs may suggest hyponatremia?
Nausea
Confusion
Lethargy
Postural hypotension (due to fluid in cells)
Reduced skin turgor (loss of free water)
Oedema/ascites (if SIADH or LF, HF N.B less barorecptor activation despite high fluid levels)
What would urine osmolality be in hyponatremia?
High if trying to get rid of water eg SIADH
Low in may be low in polydypsia or volume depletion
What would the blood results be for SIADH?
LOW serum oslomality
LOW serum sodium
LOW blood urea (it is diluted)
HIGH urine osmolality (no water)
HIGH urine sodium (not reabsorped)
How do you treat hyponatremia?
Treat underlying cause
Fluid restriction if needed
Fluid if volume depleted
Salt replacement
Loop diurtic in SIADH to reduce medullary osmolality
What do you do in severe hyponatremia
Hypertonic solution and ADH receptor antagonist